1. Field of the Invention
The present invention relates to double disc gate valves and more particularly to an improved double disc gate valve having a sealing ring and disc which can be replaced without complete disassembly of the valve.
2. Description of the Prior Art
There are innumerable designs of gate valves some of which may have been in use possibly centuries ago. With respect to the present invention, gate valves very similar to it have been in use for ten years or more. The old and new designs are almost identical, but in the old prior art design it is necessary to disassemble the whole valve in order to rebuild it because the sealing rings and internal discs can not be removed without disassembly. In order to be able to disassemble the old valve, it is necessary to remove it from its working location and take it to a repair facility. The present invention permits partial rebuilding in situ.
Gate valves are particularly adapted for use in situations where they control the flow of a fluid by being disposed in either the fully open or fully closed condition. They are not as efficient as other types of valves for regulating the volume of flow of a fluid. When a gate valve is used to control the flow of a corrosive fluid, they rapidly deteriorate and must have the seals re-established often. Generally these types of fluids are usually toxic and hazardous waste fluids.
Prior art gate valves of the type which have been used for a decade or more in situations involving corrosive fluids have required frequent rebuilding because they quickly begin to leak. Obviously, leakage is especially unacceptable where toxic and hazardous fluids are involved. It has been discovered by the inventor that partial rebuilding of a leaking valve in a particular way will in most cases stop the leak. This is done by replacing one of the internal discs of the valve and a related sealing ring. This partial rebuild or repair permits a valve to be utilized for two or three and in some cases even more life expectancies without complete rebuilding. This is a substantial savings in replacement parts and labor, and if that repair can be accomplished without the necessity of removing the valve from its working environment, additional substantial cost savings can be effected by a reduction of equipment downtime.
The realization that this improvement can be obtained is an inherent portion of this invention as well as the structure by which this result is achieved. Prior to this time it was not recognized that the valves could be renovated without removing the valve and replacing or repairing all of the parts in a complete rebuild at a repair facility remote from the operative location of the valve.